[urq] I love CIS, really !

[Louis-Alain Richard]

A contrario to the faster guys here, I really love CIS. When properly
maintained, it is reliable, clean running, and its mode of operation is
something even I can understand. However, hot start is difficult, I must
agree.

Last thursday, I replaced the last bit of 22 years old rubber that was left
on the engine, the 2in long by 3/4in diameter tube between the valve cover,
intake manifold and PCV valve. I also repaired an air leak at the fuel
distributor: the cork gasket between the air box top and the metering head
was misplaced, allowing some unfiltered air to enter.

Now, I have a question regarding the CIS operation. After correcting the 2
leaks, I did a road test: Wow!, the engine response is way more faster,
especially at low RPMs. It's like a new engine, with more low-end torque. 
Can someone explain this fact?

Secundo, I checked and adjusted idle speed and mixture. In theory, after
correcting an air leak, mixture should be richer, because there is less air
in the system, right ? Well, the duty cycle was over 60%, and idle was a bit
low. I usually keep the settings right on the factory specs, that is 44-50%
duty cycle and 850-900 rpms.
How come the mixture was leaner after correcting the leaks?

Thanks in advance,

Louis-Alain